The present invention relates to the synchronization of stereo viewing devices, particularly the synchronization of stereo glasses in multiple-end-view environments.
Stereo graphics are becoming commonplace in applications such as gaming, computer-aided design, and the like. For example, three-dimensional (3-D) computer graphics applications render separate images for a user's right eye and left eye, thereby providing the user with a stereoscopic visual experience. Real-time 3-D computer graphics render a stream of video to each eye, thus becoming a stereo video stream. One way to provide a stereo video stream is to send left and right views of a series of images to a monitor (or head or end view), where the view alternates with each frame. A user observes the video stream with a stereo viewing apparatus such as a pair of stereo glasses or goggles. Stereo glasses close a shutter over a users left eye when a right view is displayed, while a shutter over the right eye is closed when a left view is displayed. For best performance, and to avoid user fatigue, the shutters should open and closed synchronously with the stream at least 60 times per second, which requires a monitor refresh rate of 120 Hz, though lower refresh rates may also be used. Accordingly, most users set the refresh rate to the maximum supported by the monitor they are using. A stereo video stream can include non-stereo components; for example, an application program can render stereo images to a window within a computer desktop, which means the user sees a stereo scene within an otherwise non-stereo video display.
A problem arises when stereo glasses are used in a multihead system where different monitors displaying stereo graphics run at different refresh rates, or run at the same refresh rate but are not synchronized to each other. This may happen if two or more monitors have different maximum refresh rates, and are set to run at their maximum rates. If the glasses are synchronized to a stereo video stream on a first monitor having a certain refresh rate, when another stereo video stream on a second monitor having a different rate is viewed, the stream is not viewed in stereo, that is, the stream is not properly reconstructed.
Accordingly, what is needed are methods and apparatus for synchronizing stereo glasses or other viewing apparatus to a monitor that is displaying stereo content in a multiple monitor or end-view system. Also, the methods and apparatus should selectively change which video stream the glasses are synchronized to based on changes in displayed content or other information.